Diazasilene (SiNN): a comparative study of electron density distributions derived from Hartree-Fock, second-order Moller-Plesset perturbation theory, and density functional methods.

The electron densities of the 3 Σ - ground state of diazasilene (SiNN) derived from density functional methods and conventional ab initio (UHF and UMP2) methods are compared and analyzed. The spin contamination is investigated at the HF, MP2, MP3, MP4, and DFT levels. The optimized geometries and vibrational frequencies obtained by using Becke-Perdew gradient corrections to the LSDA exchange and correlation functionals are also reported. The failure of the Hartree-Fock method, and other methods in which the Hartree-Fock single determinant wave function is used as the reference configuration, to predict a bound structure for SiNN is attributed to the antibonding character of the spin density along the Si-N bond